Zach Baldwin on How Ponyfishes and Flashlight Fishes Shine

Curator John Sparks is blogging weekly about the upcoming exhibition, Creatures of Light, which opens on Saturday, March 31. This week, he invited Zach Baldwin, a Ph.D. student at the Museum’s Richard Gilder Graduate School who works in the Department of Ichthyology and who consulted on the exhibition, to contribute the guest post below.

A common misconception about bioluminescent fishes is that they all live in the perpetual darkness of the deep sea. In truth, one of the most fascinating aspects of bioluminescence is the diversity of organisms and environments in which the phenomenon is known to occur. There are bioluminescent fishes occurring on coral reefs, in estuaries, and even in the rocky intertidal zone along coastlines. Approximately 100 species in nine families of fishes that live in shallow marine waters are known to luminesce.

These include ponyfishes, a group that John Sparks studies: small, silvery fishes that occur along the coastlines of the Indian Ocean. Their bioluminescence is produced in a light organ around the throat filled with luminescent bacteria that shines light backward into the fish’s swim bladder and then out the sides or bottom through translucent “windows.” Some species also shine light out from their head, including from bizarre chin headlights. They use their bioluminescence to help attract mates and to camouflage with the ambient light of their environment. Creatures of Light will include a larger-than-life model of a ponyfish, a male Photopectoralis aureus.

Visitors to the exhibition will also be able to see a live shallow-water fish, the aptly named flashlight fishAnomalops katoptron. These nocturnal fish live over coral reefs and use their impressive headlights to attract and see prey, avoid predators, communicate to other flashlight fish, and attract mates. Their light is produced by bacteria living in pouches under their eyes, which can be swiveled in and out, giving their light a blinking appearance, as seen in this video.

For some neat footage of another shallow bioluminescent fish, check out this video of a cardinalfish “spitting” bioluminescence at 1:06.